Human life depends on a tiny fraction of the world’s water, which is constantly recycled between the oceans, land and atmosphere. Freshwater reserves are unevenly distributed, which creates water-rich and water-poor regions (in which shortages occur). Millions lack access to both safe drinking water and improved sanitation facilities and are affected by water-borne diseases as a result. Improving water quality and sanitation for the poorest requires sustainable development that uses appropriate technology and the expertise of local communities. Diseases contracted from contaminated water such as malaria and cholera are being effectively controlled in many areas. Water pollution such as marine oil slicks is a worldwide environmental issue and many countries have responded by introducing laws and agreeing to international conventions to prevent it.
CONTENTS a) Global water distribution
h) Managing pollution of fresh water
b) The water cycle
i) Managing water-related disease
c) Water supply
j) Case study: Environmental impacts of the Three Gorges Dam
d) Water usage e) Water quality and availability f) Multipurpose dam projects
k) Case study: Cleaning up the River Rhine
g) Causes and impacts of water pollution
LEARNING OBJECTIVES Describe the distribution of the Earth’s water. Describe and interpret the water cycle. Describe the sources of fresh water used by people. Describe the different ways fresh water can be used. Compare the availability of safe drinking water (potable water) in different parts of the world. Describe and evaluate multipurpose dam projects. Describe the sources of water pollution.
Describe and explain the impact of pollution of fresh water on people and on the environment. Describe and explain strategies for improving water quality. Describe the life cycle of the malaria parasite. Describe and evaluate strategies to control malaria. Describe strategies to control cholera. Describe the impact of a named multipurpose dam scheme. Describe the causes, impact and management of pollution in a named body of water.
4
Water and its management
GLOBAL WATER DISTRIBUTION The world’s total water supply amounts to approximately 1386 cubic metres. Figure 4.1 (first bar) shows that over 97 per cent of this water is saline and mostly located in the oceans. Only a tiny proportion of this total (2.5 per cent) is the fresh water that humans require to sustain life (middle bar). Of this fresh water, over two-thirds is locked up in glaciers and ice caps and almost all the rest is stored as groundwater (water in the soil or held in pores of rock). Surface fresh water (third bar), which is the source of the water people consume around the world, represents only slightly more than 1 per cent of the total fresh water available (0.0067 per cent of the Earth’s total water). Almost 90 per cent of the planet’s fresh water is stored in ice and lakes with the remaining 10 per cent being held in five other main stores. Considering that rivers are the main source of water for the world’s population, it is clear that human life depends on just 0.0002 per cent of the planet’s total water. Fresh water 2.5%
Other saline water 0.9%
Oceans 96.6%
Total global water
Surface/other fresh water 1.2%
Groundwater 30.1%
Glaciers and ice caps 68.7%
Ground ice and permafrost 69.0%
Fresh water
Surface water/other fresh water
Atmosphere 3.0% Living things 0.26% Rivers 0.44% Swamps, marshes 2.6% Soil moisture 3.8% Lakes 20.9%
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WATER AND ITS MANAGEMENT
∆ Fig. 4.1 The locations of water on Earth.
THE WATER CYCLE The volume of water on Earth has remained much the same for billions of years because it moves continuously and very efficiently around the world. The water cycle, driven by the sun’s energy, also known as the hydrological cycle, describes this movement of water between the oceans, the land and the atmosphere and is summarised in Figure 4.3. r The sun heats the water held on the Earth’s surface in oceans, seas and lakes. Some of this water is turned into water vapour (water in the form of an invisible
∆ Fig. 4.2 Victoria reservoir, Sri Lanka – rivers are the world’s most important source of fresh water.
condensation
condensation vapour transport evaporation
precipitation
evaporation
transpiration by plants
evaporation precipitation
surface run-off percolation through rocks
river lake land ocean
groundwater flow
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gas) through the process of evaporation. Some water vapour is added by plants through the process of transpiration (the evaporation of water moving through the plant from its leaves). r This warm moist water vapour rises because it is less dense than the surrounding atmosphere. As it rises the air cools and the water vapour condenses (turns back into water droplets) into clouds, which air currents transport around the globe. ∆ Fig. 4.4 Plants intercept some precipitation. r These water droplets then fall as precipitation (rain, snow, fog, mist, dew) onto the land and oceans. Some will be intercepted to provide the water that plants and humans require for their survival, for example, taken up by plant roots or collected in reservoirs. Water will also be captured and stored in freshwater lakes or in ice caps or glaciers. r Most of the precipitation, however, will flow across or run off the surface of the land and into rivers or infiltrate the ground through percolation. Rivers return the water to the oceans. Some of ∆ Fig. 4.5 Ice caps such as the Greenland ice cap will the water that seeps underground through capture and store some precipitation. infiltration will be stored in aquifers (layers of permeable rock that absorb water) while the remainder will eventually seep back into the ocean as groundwater flow.
THE WATER CYCLE
∆ Fig. 4.3 A summary of the water cycle.
many also have multiple showers, baths and toilets in additional bathrooms. Millions of litres of water are also used each year to water gardens and fill ponds. Outside of the home, many leisure and convenience activities such as swimming pools or car washes also consume large quantities of water.
∆ Fig. 4.16 A petrochemical manufacturing plant at Antwerp, Belgium.
∆ Fig. 4.17 Cooling towers of a nuclear power station at Doel, Belgium.
WATER QUALITY AND AVAILABILITY There are 42 800 billion cubic metres of freshwater reserves available on Earth, which amounts to an average allocation of 5925 cubic metres per person a year. However, this figure assumes an even distribution of freshwater reserves across all of the regions and countries of the world, which is far from the case, as seen in Table 4.3. Region
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WATER AND ITS MANAGEMENT
Latin America and Caribbean East Asia and Oceania Europe and Central Asia North America Sub-Saharan Africa South Asia Middle East and North Africa
Water reserves Available water reserves per (billions cubic metres) person per year (cubic metres) 13 867 22 162 10 096 4525 7071 7866 5668 15 993 3883 3987 1982 1152 231 554
∆ Table 4.3 Distribution of global water reserves by region.
Because of this uneven distribution, the world has water-rich and water-poor regions. South America and the Caribbean, with 500 million inhabitants or 8 per cent of the world’s population, has 31 per cent of the world’s freshwater reserves. North America is another water-rich region, with 13 per cent of the freshwater reserves but only 7 per cent of the planet’s residents. In fact just two countries – Brazil and the United States – possess 25 per cent of the world’s water reserves. Compare this with Asia where over 4 billion people live (60 per cent of the world’s population) but only have access to 28 per cent of the world’s freshwater
resources. The most water-poor regions of the Middle East and North Africa contain only 0.5 per cent of freshwater reserves and as home to 5 per cent of the globe’s population, have the lowest available water reserves per person in the world. Such an uneven distribution of water resources means that inevitably some countries experience either physical or economic water shortages, while in others there is no scarcity at all, as Figure 4.18 shows.
Water scarcity extreme physical water shortage physical or approaching physical water shortage economic water shortage little or no water scarcity no data
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A physical water shortage occurs in a country when all available reserves have been exploited and demand continues to rise. An economic water shortage means that people have insufficient water even though there are adequate water reserves available. This is often the case in the world’s lowest income countries, which commonly do not possess the capital or technology to invest in fully exploiting their water reserves. This is true in many Sub-Saharan countries of Africa. Angola is ranked by the World Bank as 116th in terms of wealth out of 183 countries and Angolans have an average life expectancy of just 50 years. Despite having potential water reserves of over 6000 cubic metres per person, less than 10 per cent has so far been exploited. Because water is the world’s most valuable natural resource, serious disagreements and even conflicts can occur between countries when its ownership and use is disputed. When in 2013 Ethiopia began construction of the Renaissance Dam project on the Blue Nile, ∆ Fig. 4.19 Cachoeiras waterfall, Angola. one of the major tributaries of the River Nile, the government of Egypt threatened to declare war. The River Nile (Figure 4.20) is fed by waters from 11 countries, and 40 million
WATER QUALITY AND AVAILABILITY
∆ Fig. 4.18 Water scarcity by country.
End of topic checklist Key terms accessibility, acid rain, agriculture, aquifer, artesian, bioaccumulation, catchment, climate change, commercial, condensation, culture, desalination, desert, disease, distribution, domestic, drought, ecology, economic development, economic recession, ecosystem, environment, erosion, eutrophication, fresh water, genetic engineering, greenhouse gas, groundwater, habitat, hazard, history, improved sanitation, improved water source, indigenous, industrialised, industry, infrastructure, location, manufacturing, migration, multipurpose dam, natural resources, nongovernment organisation, photosynthesis, pollution, potable water, precipitation, primary consumer, raw material, recycling, religion, renewable energy, run-off, rural, secondary consumer, sedimentation, services, subtropical, surface water, sustainability, tertiary consumer, trade, transport, trophic level, tropical, urban, water cycle, water-poor, water-rich, water table
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WATER AND ITS MANAGEMENT
Important vocabulary aid, algae, antibiotic, aquatic, arable, archaeological, atmosphere, bacteria, basin, brackish, canyon, capital, charity, commodity, compensation, compost, consumer, contamination, convention, coral, dam, dehydration, deoxygenation, depletion, detergent, diagnosis, directive, disinfected, dispersant, earthquake, economic, electricity, elimination, endangered, energy, eradication, estuary, evaporation, export, extraction, faecal, fault, fertiliser, flood, glacier, hormone, hydraulic, hydroelectric, hydrologist, ice cap, impact, impermeable, infection, infiltration, insecticide, intensive, irrigation, joint, lake, landscape, latrine, law, leaching, lock, malaria, migration, mining, mobility, mosquito, mutation, navigation, nuclear, nutrient, ocean, organic, parasite, pathogen, percolation, permafrost, permeable, permit, pesticide, physical, phytoplankton, porous, productivity, prophylaxis, rapids, regulation, rehydration, remote, replenish, reserve, reservoir, resettlement, resistance, resistant, river, saline, saturated, season, seasonal, sedimentary, sewage, silage, silt, sludge, slurry, soil, spawn, spring, subsistence, tax, technology, toxins, transmission, tributary, turbine, vaccine, valley, waste, weir, wetland
During your study of this topic you should have learned:
â?? All human life depends on a tiny fraction of the world’s total water. â?? The water cycle describes the constant movement of water between the oceans, land and atmosphere.
End of topic checklist continued ❍ Groundwater and surface water are the two main sources of water for human use. ❍ Desalination involves removing dissolved salt from sea and brackish water to make it fit for human consumption.
❍ Water consumption varies hugely between different regions of the world. ❍ The level of economic development in a country is the main factor affecting water consumption.
❍ Freshwater reserves are not distributed evenly across the world, which means that some regions can be defined as water-rich and others as water-poor.
❍ Water shortage can be the result of physical or economic factors. ❍ One in ten people do not have access to potable or improved drinking water and this can be the cause of serious water-borne diseases.
❍ Countries with poor access to potable water also often have poor sanitation, which increases the risk of disease.
❍ Multipurpose dams such as the Three Gorges Dam in China are constructed for a range of reasons, including providing energy, irrigation and drinking water and improving river navigation.
❍ Multipurpose dams can have positive and negative economic, social and environmental impacts.
❍ Domestic waste and industrial and agricultural practices are the main sources of water pollution.
❍ Supporting appropriate and sustainable developments in the poorest countries
of the world is the most effective way of improving sanitation and water supply.
❍ Oil spills such as the Deepwater Horizon blowout can have catastrophic ecological and economic consequences, and disaster planning and management is required to minimise these effects.
The questions for Section 4 start on page 247.
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but a range of measures have now been introduced to combat their transmission and achieve eradication in the future.
WATER AND ITS MANAGEMENT
❍ Many countries now have strict controls and laws to prevent water pollution. ❍ Water-related diseases such as malaria and cholera kill millions of people a year
Despite these threats the number of wild mountain gorillas has increased over the past 20 years and now stands at 880 individuals. This is the result of the success of the International Gorilla Conservation Programme (IGCP), which has been working since 1991 to ensure its long-term survival. Particularly effective conservation measures include:
t Providing funding to increase both the
number and improve the equipment of anti-poaching patrols in protected forest areas. This has increased the coverage and duration of patrols and reduced significantly the number of animals being poached.
∆ Fig. 9.40 Rangers at Volcanoes National Park, Rwanda, which has the largest population of wild mountain gorillas in the world.
t Organising and funding teams to collect
hunting snares and bush meat traps from the forest.
t Setting up rehabilitation centres where
orphaned or rescued young gorillas can be prepared for a return to the wild.
t Increasing the area of national parks to
protect more forest and undertaking afforestation work in cleared areas to allow lost habitat to regenerate.
∆ Fig. 9.41 Cleared forest now used as farmland adjacent to Volcanoes National Park, Rwanda.
t Better management of visitors and tourists to
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NATURAL ECOSYSTEMS AND HUMAN ACTIVITIES
minimise the likelihood of disease transmission by ensuring that they are always more than seven metres from gorillas.
t Working with local communities to increase
understanding of gorillas and support for their protection and conservation. Teachers and pupils have been given information books about gorillas, and rangers run awareness and conservation programmes in local schools.
∆ Fig. 9.42 Male ‘silverback’ mountain gorilla in the forest of the Virunga mountains.
t Encouraging ecotourism and investing profits from visitors viewing gorillas back into the local community, for example, building new schools and clinics. As a result, people have come to see the monetary value of conserving the forest habitat and actively protecting gorillas.
∆ Fig. 9.43 Developing ecotourism is an important aspect of mountain gorilla conservation programmes.
CASE STUDY
UNESCO BIOSPHERE RESERVE, NORTH DEVON, UK
North Devon’s biosphere reserve covers much of the ecosystem created by the catchment areas of the Rivers Taw and Torridge and the offshore marine areas stretching out to Lundy Island in the Bristol Channel. Located in the county of Devon in the UK, it is home to about 150 000 people and includes protected landscapes of great ecological and landscape value. However, the majority of the area is ∆ Fig. 9.44 North Devon Biosphere logo. where people live and work. Lowland farmland is the most important land use.
Br istol
Channel
Biosphere Region Zones
■ Buffer ■ Core ■ Transition
Ilfracombe Lundy Island
Minehead
North Devon Biosphere Buffer Zone
Braunton Burrows
Barnstaple Bay
SOMERSET Exmoor National Par k
Barnstaple
(Bideford Bay)
w Ta
Northam Bideford
ge rid Tor
D E V O N Tiverton
Nature Improvement Area Holsworthy
0
∆ Fig. 9.45a The UNESCO Biosphere Reserves of the United Kingdom.
1 km
Exeter
C O R N WA L L
Dar tmoor National Pa r k
∆ Fig. 9.45b North Devon biosphere reserve.
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The core area consists of Braunton Burrows, which is a unique sand dune system habitat of hundreds of flowering plants designated as both a Special Area of Conservation and a Site of Special Scientific Interest. Management of this area focuses on ensuring the protection and enhancement of the sand dunes and its adjacent coastal habitat, which includes a coral reef with a diversity of coral and marine life seen nowhere else in the UK and the Taw and Torridge estuary, which is an important feeding ground for long distance migratory birds.
CASE STUDY
The North Devon Biosphere Partnership is the body responsible for coordinating the management of the reserve in line with the vision and objectives of an agreed strategy for the years 2014–2024. The partnership works closely with willing local communities to manage the environment sustainably in ways that will conserve unique habitats, generate income, reduce poverty and improve the health and wellbeing of people.
19. Draw a labelled diagram to show three different ways in which soil erosion can be controlled and reduced by farmers. 20. Define what is meant by sustainable agriculture. 21. What does the biocontrol of pests and diseases mean? Describe an example of one kind of biocontrol used on sustainable farms. 22. In 2012, three researchers (Gaybullaev B, Chen and Gaybullaev D) published their results of fifty years of hydrological measurements of the volume of water in the Aral Sea. Date 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Water volume in cubic kilometres 1093 1007 925 786 664 502 327 239 149 112 98
Citation: Gaybullaev, B., Chen, S. & Gaybullaev, D. Appl Water Sci (2012) 2: 285. doi:10.1007/s13201-012-0048-z a) Draw a simple line graph, bar graph or histogram to show the changes which occurred between 1960 and 2010. b) By what proportion did the volume of water shrink in the Aral Sea between 1960 and 2010? c) Which five year period saw the greatest absolute decrease in the volume of water? d) Which five year period saw the single greatest proportionate loss of water?
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END OF TOPIC QUESTIONS
e) Explain the main causes of the depletion of water in the Aral Sea over this time period.
Answers to these questions can be found at the back of the Teacher Guide.
4. Water and its management questions 1. Name four stores of surface water on Earth. 2. What important natural process does the water cycle describe? 3. On a copy of the summary diagram of the water cycle below, write in the following missing labels in their correct position: precipitation (used twice), vapour transport, transpiration by plants, percolation through rocks and groundwater flow condensation condensation .....................................
evaporation
.....................................
evaporation
.............................................
evaporation .....................................
surface run-off river ................................... ...................................
lake land
ocean
...................................................
4. In your own words, and using a diagram to help, explain how water is extracted from underground aquifers. 5. Explain why groundwater reserves in some part of the world are being depleted. Describe with an example some of the effects of groundwater depletion.
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7. What does desalination involve? Why is desalination not more widely used around the world at present?
END OF TOPIC QUESTIONS
6. Las Vegas in Nevada in the United States is facing a water crisis. What has caused this crisis and what is the city trying to do to solve it?